"The results are in. We have won," Clark told his supporters shortly after 10:30 p.m. (11:30 p.m. ET).

"I tell ya what, as an old soldier from Arkansas, I just couldn't be prouder of the support in this first election that I've ever won."

Unofficial results show Clark with a lead of less than 1 percent -- just 1,275 votes. The final results of the race will be certified in a week

Clark, a retired general, had been locked in a tight race with Sen. John Edwards of North Carolina for much of the night but appeared to pull ahead as the final precincts reported results.

Clark has spent most of the past week campaigning in Oklahoma. Expectations were high because of the time and money he spent in the state, and because it's a neighbor to his home state of Arkansas.

Although Clark has held leadership positions, including serving as NATO's supreme commander, he had never competed in an election until New Hampshire's primary January 27.

Clark finished third in that race.

He has been criticized for coming to the Democratic Party late in life. He has acknowledged voting for Republicans Richard Nixon and Ronald Reagan, but said he voted for Bill Clinton and Al Gore.

He again addressed the issue in his speech to supporters.

"There is no party more committed to the American people. No party more committed to lifting people up than this party, my party, this Democratic Party," he said.

He continued his speech to cheers.

"George W. Bush has had three years to keep our country moving forward. He's moved it in the wrong direction. He's set us back," Clark said. "Three million lost jobs. Forty-four million Americans without health insurance. An unnecessary war that's resulted in a mess in Iraq. It's time we brought real Democratic values back to America."

Clark, a Rhodes scholar and West Point graduate, works as an investment banker in Little Rock.